Corrosion inhibition



United States Patent 3,449,262 CORROSION INHIBITION Wesley L. Archer and Miriam Hatter, Midland, Mich., as-

siguors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware 3,449,262 Patented June 10, 1969 The amount of benzoate salt incorporated into the methyl chloroform may vary widely. Only an amount suflicient to give the desired degree of corrosion reduction is required. Amounts in excess of that required to form a saturated solution may be used. Corrosion rates N0 Dl'aWillg- Filed J31!- 1966, 523,561 5 are decreased using relatively low concentrations of ben- (33f 11/14, 11/12 zoate salt inhibitors, generally from about 0.1 ppm. to 252-396 4 Cla'ms 3000 p.p.m. of the metal ion as the benzoate salt based upon the total weight of the methyl chloroform-containing composition. The benzoate salt inhibitors are com- ABSTRACT OF THE DISCLOS RE patible with other types of inhibitor systems. For example, Methyl chloroform is stabilized to prevent corrosion ben z9ate SaltF may be f l y chloroform f iron in the presence of Water by the inclusion f an positions which arealready 1nh1b1ted specifically to preinorganic benzoate or naphthoate wherein the inorganic P? of the methyl chloroform by cation is any of various multivalent metals and the am- 15 P1011 Wlth alumlmum aRd/OI other metals, Zlnc, rnonium group. iron, brass etc. The addition of such benzoate salts prevents the loss or destruction of other inhibitors (such This invention relates to the preparation and use of 3 2232 3 222; gg g gfi zg g i t g igii r e e ue of a methyl chloroform composition which is 1nh1b1ted with presence of and W f h l nitromethane against the action of aluminum (but not gg i g sig g gi fi g i ggig f i g pgfii g against iron corrosion) results in a loss of inhibitor due 2 products in addition to inorganic iron oxides and/or g f Induced by the products of the corro gg gg gg g g za fif sfisgifig g g gi g gg i; The benzoate s alt inhibitorsare elfective in retarding lytic action of the iron compounds initially formed. corroslon when Incorporated 1pm a-system c9ntammg According to the present invention, the corrosion of i i gfif i sg ggg s l gi i 53 2 :1 iron in th resence of meth l chloroform and at least a catalytic afnount of water i: retarded by incorporating PO abol-1t 5 25 perce-n-t by Welght of Water) result an inhibiting amount of certain benzoate salts into the lnev-erslble decomposmqn of the methyl chlorQform Wlth the slmultaneous formation of unwanted organic products methyl chloroform f p Salis which may be such as vinylidene chloride and polymers of indetermiare represented byt 6 10m: 0mm a nate structure. The benzoate salt inhibitors effectively M+ (A) prevent the formation of such organic decomposition wherein M is a metallic element or an ammonium group prodllcts by retarding the corrosion reaction of the iron with a valence of n (wherein n is an integer of from 1 to In this System 6), and represents the benzoate anion (cqHsozyl The benzoate salt in ibitors are especially effective a naphthoate anion (C I-l O or a nuclear-substituted m the i h phase up to temperatures at whlqh thermal benzoatc anion containing from 1 to 5 monovalent 40 decomposition of methyl chloroform occurs (1.e., about stituents (which may be the same or different) wherein 2 1 b d f h each substituent is selected from the group consisting of e o .owmg examp es are mute or t e B a halogen (Cl, Br, I, F) NO2, phenoxy and a c142 of illustration only and are not to be construed as limiting alkyl group. A preferred group of benzoate anions (A) the scope of the mventlon In is represented by the formula: Examples 1-32-General Method Solutions were prepared (total volume of milliliters) composed of 0.5 percent by weight of water, a given Ru concentration of benzoate salt inhibitor and the remain- 50 der methyl chloroform. Polished iron nails (AISI-SAE classification number 1025 steel with about 0.25 percent wherein n is an integer of from 0 to 5 representing the carbon) 2.5 inches long and inch in diameter, were number of nuclear substituents, each R is independently added to each sample. Each solution was added to a selected from the group consisting of Cl, Br, N0 phenfour ounce test bottle. A plastic seal was placed under oxy, and an alkyl group of from 1 to 12 carbon atoms, the cap of the test bottle to prevent evaporation before and every unsubstituted nuclear carbon atom is bonded the cap was sealed. The sample bottles were large enough to a hydrogen atom. Suitable metal elements which may to enable about /3 to /2 of the length of the nail to form the cationic portion of the salt include magnesium, protrude from the surface of the methyl chloroform comscandium, lanthanum, titanium, chromium, manganese, positions. The samples of Wet methyl chloroform in coniron, cobalt, nickel, zinc, aluminum, tin, lead, tellurium, tact with iron were then heated in an oven at a temperacerium, europium and gadolinium. Compounds in which ture of approximately 57 C. for a period of seven days. the metal moiety is in a stable (usually higher) valence Controls composed of wet methyl chloroform in contact state are preferred in the system. For convenience, the with iron, but without benzoate salt inhibitors, were carterm benzoate salts is defined to include salts of both ried through the same procedure. After seven days, the substituted and unsubstituted benzoates, including the samples were examined to determine the extent of the naphthoate grou iron corrosion. The samples were rated as follows:

Agigity Property measured Sygn a b l Explanation 0 No corrosion inhibition.

Slight corrosion inhibition. 2 Good corrosion inhibition.

TABLE II Weight Concen- Concentration (parts per million ppm. as the metal Salt ion) Activity Example Number:

26 Cobalt (II) p-phenoxy benzoate 50 2 27.-. at 50 2 28.-- Cobalt (II) p-dodecyl benzoate 50 2 29". Cobalt (II) p-nonylbcnzoate 50 2 30... Manganese (II) p-njtrobenzoate 1 2 31 Manganese (II) 2,5-tlimethylbenzoate 190 2 32 Manganese (11) p chlorobenzoate 6 2 No inhibition.-Iron sample covered with a heavy crusting of a mixture of organic and inorganic corrosion products.

Slight inhibition-Some areas of iron sample remain clean; colored film may form.

Good inhibition-Clean shiny surface; may be a few small spots of discoloration. No crust formation.

The results are summarized in Tables I and II. The methyl chloroform employed in Examples l21 and 26- 32 was commercial grade containing the following ,inhibitors (all percentages by weight): (1) 3.5-4.0 percent dioxane; (2) 0.5 percent nitromethane; and (3) 0.5 percent butylene oxide. For comparison purposes, pure (99.3 percent) methyl chloroform containing no inhibitor was employed in Examples 2225. In a similar manner, typical substituted benzoate salts were employed as corrosion inhibitors in Examples 2632 (summarized in Table II).

TABLE 1 Weight Concentration (parts per million ppm. as the metal ion) Benzoate Salt of- Activity Example Number:

1 Aluminum (III) Ammonium (I) Ferrous (II) Gadolinium (III) Langhanum (III) 1 Based on NH 3. 7 The symbol indicates an approximate concentration.

We claim as our invention:

1. Methyl chloroform stabilized against iron corrosion in the presence of water by having incorporated therein an inhibiting amount of a salt of the formula wherein:

(a) n is an integer of from 1 to 6,

(b) A is selected from the group consisting of the benzoate anion, the naphthoate anion, and a nuclear substituted benzoate anion in which each substituent is independently selected from the group consisting of: a halogen, nitro, phenoxy, and a C alkyl, and

(c) M is selected from the group consisting of magnesium, scandium, lanthanum, titanium, chromium, manganese, iron, cobalt, nickel, zinc, aluminum, tin, lead, tellurium, cerium, europium, gadolinium, and NH 2. A composition in accordance with claim 1 wherein the concentration of the salt is from about 0.1 part per million to 3000 parts per million based upon the total weight of said composition.

3. A composition in accordance with claim 1 which contains up to 10 percent by weight of water.

4. A method of inhibiting the corrosion of iron in the presence of methyl chloroform and water which comprises contacting the water-methyl chloroform mixture with an inhibiting amount of a salt as defined in claim 1.

References Cited UNITED STATES PATENTS 2,395,307 2/ 1946 Weber et a1. 2,472,503 6/ 1949 Van der Minne et al. 252-396 2,598,496 5/1952 Bradley et al 260-515 2,959,623 11/1960 Drag et al 260-6525 3,265,747 8/ 1966 Cormany et al 252-407 LEON D. ROSDOL, Primary Examiner.

W. SCHULZ, Assistant Examiner.

US. Cl. X.=R. 

